The Battle of Theramore, and specifically the use of the Mana Bomb, was actually a catalyzing event that led straight to Vol'jin's insurrection against Garrosh and his True Horde forces. So yes, many Orcs - an overwhelming majority of the Horde in fact, did indeed rebel in the wake of the Battle of Theramore. It seems like you're trying to revise history on a pretty extreme level.